Spark-gap.



C. E. CAMPBELL.

SPARK GAP.

APPLICATION FILED APR.24,1916.

Patented June 26, 191?.

3 SHEETS-SHEET I.

c. E. CAMPBELL.

SPARK GAP.

APPLICATION FILED APR. 24. HHS.

' LQMAEWW Patented me 26,1917.

3 8HEETSSHEET 2.

In Irv/722m:

.c. E. CAMPBELL. S PARK GAP. APPLICATlON FILED APR.24, I916.

LQSIAW. Patented June 26, 1917.

3 SHEETS-SHEET 3.

To all whom it may concern:

Be it known that I, CHARLES E. CA PBELL, a citizen of the United States,residing at Lynn, in the county of Essex and State of Massachusetts,have invented certaln new and useful Improvements in Spark-Gaps, ofwhich the following is a specification.

My invention relates to improvements in spark gaps, and the object of myimprovement is simplicity and economy 1n construction and convenienceand eificlency in use.

In the accompanying drawing Figure 1 is a side elevation of my improvedspark gap.

Fig. 2 is a front end elevation of the same.

Fig. 3 is a plan view of the same with the guard cage removed.

Fig. 4 is a sectional view, on an enlarged scale, on the line 02 a: ofFig. 3. I

Fig. 5 is a similar view on the line 3 3/ of Fig. 3.

Fig. 6is a front elevation of the movable member and the frame.

Fig. 7 is a fragmentary plan view of the base, showing the hollow studfor supporting the post.

Fig. 8 is a side elevation on the same scale as Fig. 1 of a form ofimproved spark gap showing a double pair of gaps with the moving partsconnected by gearing.

Fig. 9 is an end elevation of the same.

Fig. 10 is a plan View of the same, the cage being omitted.

Fig. 11 is a rear elevation of the movable portion and adjacent parts.

Fig. 12 is a sectional view on the line .2 z of Fig. 10.

Fig. 13 is an end elevation, on an enlarged scale, of a modified form offrame'and adacent parts, showing a spring steadying device across thebreak in the annular body portion.

Fig. 14 shows an adaptation of the same feature to a spark gap of thedouble gap construction.

My improved spark gap comprises a pair ofstationary contacts orelectrodes 10 that operate in cooperation with a movable con- 1peripheryby aplurality of longitudinal are 15.

l. E. CBELL, 0F LYNNQMASSAUfiETTS- n-e. r

Specification of Letters Patent. Patent gfl Jung 2%, 1291i? Applicationfiled April 2%, 1916. Serial No. 93,195.

A pair of electric line terminals 16 suitably positioned on the base 12are connected by connecting strips 17 underneath the said base 12, oneto each of the supporting posts 18 of the fixed contacts 10.

Considering the fixed contacts 10, these comprise each the post 18,extending upwardly from the base 12, and supporting by its upper end andon the inner side thereof, an inwardly directed composite member,composed on the exterior of the fixed contact proper or contact piece 19at the extreme inner, free end and'intermediate the said contact piece19 and the supporting post 18 a filling of washers forming a heatradiating member 20. The said radiating member 20 comprises a set ofradially positioned washers having alternately a large washer 21 and asmaller washer 22, a plurality of such washers being used suflicient toprovide the desired heat radiating effect.

As a support for the post 18 on the base 12 and providing electricconnection therewith I provide the hollow stud 23 positioned in asuitable hole in the base 12, and secured by the nut 24, the latterbeing on the under side of the base 12, and bearing against theconductor strip 17 The bore 25 of the stud 23 is screw threaded, and thehead portion 26 is preferably housed in a suitable recess on the upperside of the base 12.

Thus the hollow stud 23 is fixedly secured to the base 12 and apermanent connection therewith is made leading to the terminal 16, andmeans are provided in the threaded bore 25 for receiving the holdingscrew 27 that holds the post 18 in position.

The body portion of the post 18 is hollow, having a longitudinal bore 28that is a fit for the screw 27 The said body portion has a square crosssection, and on the lower end has a downwardly projecting positioningpin 29 that engages with a suitable hole 30 in the base 12. In drillinginto the base 12 to form the hole 30 I prefer to cut into the head 26 ofthe stud 23 to form a notch 31 for engaging with the said positioningpin 29.

The holding screw 27 extends entirely through the post 18, the headbeing engaged with the upper end thereof, and the lower end beingscrewed into the threaded bore 25 of the stud 23 and serves to hold thepost 18 in place, the positioning pin 29 determining the angularposition thereof.

At the upper end of the post 18 there is a trans\-'crse bore 32, havinga screw thread in which is screwed the outer end of the solid stud 33.The bore 28 in the post 18 extends through the said solid stud 33, sothat the holding screw 27, which is positioned in the said bore extendsacross the said stud 33 and serves to hold the same positively in thesaid transverse bore 32.

The other end of the solid stud 33 extends inwardly from the post 18 andserves as the support for the composite member mcntioned. being directlyconnected to the outer end ofthe radiating member 20.

The said radiating member 20 which as stated above comprises on theexterior the washers 21 and 22, is a unitary structure. The sameconsists of a core 34 in the form of a hollow sleeve, internallythreaded, the washers 21 and 22 being mounted on the exterior thereof,and the ends of the core 34 being headed over against the end washers,the holes in the end washers being preferably tapered on the outer sidesto receive the headed or turned ends and to permit of finishing the sameflush with the outer faces of the said end washers. This permits theouter end washer 21 to bear against the opposed face of the post 18.

The threaded core 34 is engaged by the outer end with the overhangingend of the solid stud 33 and by the other, inner end is engaged withanother solid stud 35, which latter serves as a connection and supportfor the contact proper 19, which is in the form of a cap nut. A washer36 may be interposed between the contact nut 19 and the radiating member20.

The outer contact or sparking faces 37 of the two contact nuts 19 arefaced ofi in a common plane, at right angles to the axes, after theparts have been adjusted and secured in their final positions.

It will be noted that the construction of the fixed contact structure issuch that the several parts can be readily removed, beginning with thecontact nut 19 and following through the successive parts, even todismantling the entire post structure, and the latter may be effectedwithout disturbing the electrical connections leading to the lower endsof the post 18.

The movable contact structure comprises the movable contact member oradjusting part 11 and the frame or casing 38 by which the same isadjustably supported by means of screw thread engagement.

The said adjusting part 11 comprlses a solid core 39 in the form of anelongated member having a screw thread on the periphery, on which aremounted a handle 40 at the outer end, a dial 41 at the other end in theform of a relatively large disk,-having a screw thread on theperiphery-47, and adjacent and opposed to the said dial 41 and extendingan appreciable distance along the core toward the handle 40, a set ofradiating washers, designated generally by the character 42, held inplace by a nut 43. The said set of washers comprises large washers 44alternating with smaller washers.

For the smaller washers I prefer to use two sizes to produce a steppedeffect, those on the side toward the nut 43, designated by the character45, being of the smaller size, and a plurality on the side toward thedisk 41, designated by the character 45, being more nearly of the sizeof the large size washers 44 with which they alternate, as shown.

The construction described provides a superior backing for the disk 41,and extra heat conducting material adjacent the same, and serves todistribute the heat better along the heat radiating structure than wouldbe the case if the intermediate filling washers were all of the smallersize.

A disk 41 has a screw threaded hole in the middle by which the same isscrewed on the end of the core 39 and a longitudinally directed screw 46serves as a key and general locking means therefor, the same beingengaged with a threaded hole at the junction of the periphery of thecore 34 and the opposed wall of the hole in the disk 41.

The disk 41 is of appreciable thickness so that a plurality of threadswill be provided on the periphery 47, which threads are preferablyrelatively fine, being of short pitch which permits of relatively fineand accurate adjustment,

The frame 38 is in the form of a single casting having an annular bodyportion and feet 48 by which the same is secured to the base 12. Theinterior of the said body portion is threaded to fit the threadedperiphery 47 of the disk 41, and the same is of sufficient length toprovide for the desired range of adjustment.

Furthermore, the said body portion is provided with a radial slit 49 inthe side Wall provided by cutting away a small portion of the said sidewall, as shown.

The purpose of the slit or slot 49 is to provide a slight amount of giveor leeway responsive to slight changes in dimension of the parts, suchas may follow from heating of the disk 41 and connected parts, and thusto insure free turning movement of the disk 41 under all workingconditions. While the frame is made of cast material, the same hassufiicient resiliency for the conditions mentioned.

The inner contact face of the disk 41, which is opposed-t0 the fixedcontact faces 37, is faced off radially concentric with the axis of thethreaded periphery in parallelism with the plane of the said fixedcontact faces 37 Thus by turning the handle 40 there will be a trueshortening or lengthening of the change the length of the two gapscontributes to the accuracy of adjustment obtainable.

Furthermore the heat conduction away from the disk 41- is facilitated bythe large diameter thereof and this makes contact by the periphery withthe frame by which it is supported, so that the frame may be effectivein conducting away excess of heat.

Furthermore, the frame 38 may be provided with a radialrib 51 on theperiphery -to effectively radiate heat.

The base 12 may be made of marble, slate, or other suitable insulatingmaterial.

The lineterminals as described lead to the fixed contacts and themovable contact;

which is mounted in a base of insulating material and without directelectrical connect-ions, serves to electrically bridge the fixedcontacts, forming a gap with each of the same.

The two aps are accordingly operatively in series, and when anyadjustment is effected the length of both gaps is changedsimultaneously, the effect of a movement of the movable gap beingdoubled in the corresponding change in the effective length of thedouble gap.

Furthermore. such change is particularly accurate and-positive for thetwo individual gaps because of the manner of construction andarrangement described.

The apparatus described is used in connection with X-ray apparatus, andI find there are advantages in using the same in having a series ofsmall gaps in lieu of one longer gap, as a higher voltage is required tojump the gaps, and after the jump has been made, there is lessresistance, so that a fatter spark or spark of greater amperage isobtained.

The arrangement described of having a unit consisting of a singlemovable element bridging a pair of stationary contacts or electrodes maybe amplified by providing a plurality of such units, each having itsindividual movable .element bridging a pair of stationary contacts, andthe several movable elements being connected by gearing and operated inunison by means of a single handle.

Thus in Figs. 8, 9, and 10 is shown a pair of such units, mounted on asingle base 12, the two movable contacts or electrodes 11 beinginterconnected by a pair of gear wheels 52 mounted on the respectiveshafts 39 and 39*.

One of the shafts, the rear shaft 39 shown in Fig. 10, is provided withthe handle 40, the other shaft 39 being without a handle.

The gears 52 are made of insulating material such as bakelite or a builtup material composed largely of asbestos or mica. v

The rear or handle shaft 39 differs from the shaft 39 shown in Figs. 1and 4 only in the provision for mounting the gear 52, the

thread on the periphery being right handed. In the case of the frontshaft 39", the same differs from the rear shaft 39 in the omission ofthe handle.

The rear disk or dial 41, mounted on the rear shaft 39, and engaged withtherear frame 38', and which constitutes the rear contact proper, islike the disk 41 shown in Figs. 1, 4 and. 5, having a right handed screwthread 47. I

In the case of the front disk 41 and front frame 38 however the screwthread 47 is left handed.

By having the threads 47 and 47 difierent as described the travel of thetwo movable contacts 11 will be similar, when the handle 40 is turned,so that both will travel toward or away from the fixed contacts 10according to the direction the handle is turned.

The outer fixed contacts 10 are connected to the line terminals 16 onthe base 12 and the two inner fixed contacts 10 are interconnected insome suitable manner, as by a connecting strip 53 as shown in Fig. 8.

The frames 38 and 38 that support the disk portions of the movablecontacts may have the annular body portion slabbed off as shown at 56 onthe sides that are opposed to one another to provide increased air spacebetween the frames.

Also the laterally projecting feet 48 are omitted on the opposed sides,and in lieu thereof on each frame there is provided a foot 48?positioned inwardly appreciably, to increase the leakage distance -alongthe base 12*, and having a threaded hole 54 for receiving a screw 55inserted through the base 12 from the underside.

In Fig. 13, the frame 38 is provided with a steadying device across theradial slit 49 in the form of a sprin 60, mounted on a screw 61, andsupporte by cars 62 extending outwardly from the frame body, one on eachside of the slit. The hole 63 in the lower ear 62 is threaded and thehole 64 in the upper ear 62 is a fit for the body of the screw 61, thespring being positioned between the upper ear 62 and the head of thescrew.

In Fig. 14 is shown an adaptation of the feature of the spring steadyingdevice shown in the single unit construction of Fig. 18 to the duplexconstruction. In this con- 'struction the radial slit between the ears62,

designated as 41, is at the top of the frames 38 and 38, the screw 61and spring 60 being arranged as in Fig. 13, the screw heads beingdirected outwardly in each case so as to be readily accessible.

I claim as my invention 1. A spark gap comprising a pair of stationaryelectrodes and an adjustable elec trode cooperating therewith, the saldadjustable electrode bein in the form of a disk, rotatively mounte thesa1d fixed electrodes being positioned side by side and opposed to oneface of the said disk, and the supporting means for the said ad ustableelectrode comprising a frame that 1s engaged with. the periphery of thesaid disk.

I 2. A spark gap comprising a pair of stationary electrodes and anadjustable electrode cooperating therewith, the said adj ustableelectrode being in the form of a disk, rotatively mounted, the saidfixed electrodes being positioned side by side and opposed to one faceof the said disk, the supportlng means for the said adjustable electrodecomprising a frame that is engaged with the periphery of the said disk,and the sald frame having screw thread connection with the saidperiphery.

3. A spark'gap comprising a pair of stationary electrodes positionedside by side and in spaced relation and a third electrode in the form ofa disk having one face opposed to the said stationary electrodes, and

a frame serving as a support for the said.

disk and having screw thread connection with the periphery thereof.

4. In a spark gap device, a base, electrodes supported from the saidbase comprising a pair of stationary electrodes and an adjustableelectrode, the said stationary electrodes comprising each a terminalface at one end, a supporting post at the other end, and mtermediate thesaid endshaving a body portion provided with heat radiating disks, andthe said adjustable electrode comprising a disk at one end that servesas the electrode proper and that is engaged with supporting means, andhaving outwardly from the said disk a stem that is provided with heatradiating disks.

5. In a spark gap device, an adjustable electrode in the form of a disk,and a frame supporting the said disk, the said frame comprising anannular body portion having screw thread connection with the peripheryof the said disk, and the said frame having a radial slot extendingacross the side wall of the said body portion. A

6. In combination in a spark gap, having an adjustable electrode havinga cylindrical periphery provided with a screw thread and a frame havinga bore provided with a screw thread for cooperating with the saidperipheral screw thread, and the wall of the said frame inclosing thesaid electrode contact being interrupted by a radial slot, whereby. freecooperation of the parts is permitted under slightly varying relativedimensions thereof.

7. In a spark gap device, an adjustable electrode in the form of a disk,and a supporting frame, the said disk having a cylindrical peripheryprovided with a screw thread, the said frame comprising a. cylindricalbody portion having a bore provided with a screw thread for engagingwith the said periphery of the disk, and the said frame being providedon the periphery with a radial, heat radiating rib.

8. In a spark gap comprising a base and a'line terminal and a stationaryelectrode mounted thereon, a conductor strip connecting the said lineterminal. and fixed electrode, and a hollow stud fixedly mounted on thesaid base, connected to the said strip, and having the bore portionthreaded suitably to receive supporting means for supporting the saidfixed electrode.

9. In a spark gap, a base, an interiorly threaded hollow stud fixedlysecured to the said base, a stationary electrode comprising a post andan electrode proper mounted on one side thereof, a solid stud serving asthe support for the "said electrode proper and extending through thesaid post, and a holding screw extending longitudinally through the saidpost and pasing through the ,said solil stud and engaged with thesaid'hollow stu 10. In a spark gap, a stationary electrode supportedfrom a-base and comprising a post and having on one side of the saidpost a radiating member and an electrode proper, the said radiatingmember being in the form of a unitary structure, comprising a sleevehaving a screwthread on the interior, a set of washers mounted ontheexterior of the said sleeve, and the ends of the said sleeve headed overto hold the said washers in place, a solid stud screwed into the ends ofthe said sleeve and having projecting portions extending beyond the sameat each end, one of the said projecting portions being engaged with thesaid post, and the said electrode proper being mounted on the other ofthe the said projecting portions.

11. A spark gap comprising a plurality of units mounted on a singlebase, each of the said units being composed of a pair of fixed pairs offixed electrodes which they serve to bridge.

12. A spark gap comprising a pair of units mounted on a single base,each of the said units being composed of a pair of fixed 10&

electrodes and a movable electrode operatively bridging the said fixedelectrodes, the said movable electrodes being mounted so as to adjustthe gap by a-rotative movement, and gearing serving to interconnect thesaid movable electrodes.

13. A spark gap comprising a pair of units mounted on a single base,each of the said units being composed of a pair of fixed electrodes anda movable electrode operatively bridging the said fixed electrodes,threaded means serving to support each of the said movable electrodes,and gearing interconnecting the said two movable electrodes comprisngintermeshing gear wheels.

14. In a spark gap comprising two movable electrodes each bridging apair of fixed electrodes, screw threaded means supportin each of thesaid movable electrodes, eac of the said movable electrodes beingprovided with a gear wheel, the said gear wheels being in engagement onewith the other and the said screw threaded means comprising a righthanded screw thread for one of the said movable electrodes and a lefthanded screw thread for the other of the said movable electrodes.

15. In combination in a spark gap, having an adjustable electrode havinga cylindrical periphery provided with a screw thread and a frame havinga bore provided with a screw thread for cooperating with the saidperipheral screw thread, and the wall of the said frame inclosing thesaid adjustable electrode being interrupted by a radial slot, and aspring steadying device serving to resiliently bridge the said slot.

CHARLES E. CAMPBELL.

Witnesses:

LAWRENCE E. Go'rr, GUs'rAvE E. ANDERSON.

